Light signal



Dec. 12, 1944. e. R. PFLASTERER LIGHT SIGNAL Filed Oct. 28, 1942' l N V E N T O R George A. Pfi 6 a1 'ze e BY- 1? HIS ATTORNEY Patented Dec. 12, 1944 UNITEDI'STATTES PATENT mm LIGHT SIGNAL George R. Pflasterer, Greenville, Pa., assignor to The Union Switch and Signal Company, Swissvale, Pa., a corporation of Pennsylvania Application October 28, 1942, Serial No. 463,658

' Claims. (o1. 177-327) My invention relates-to light signals,v and has particular reference to light signals of the searchlight type incorporating means for projecting a pluralitylof difierently colored indications from an optical system employing a single source of light. More particularly, my invention relates to the provision of novel and improved means in such signals for projecting a plurality of differently colored indications having relative intensities independent of the coefficients of transmission of the colored filters employed to provide the different indications.

A searchlight type signal comprises an optical unit which has a single lamp as a source of light, and an operating mechanism for selectively interposing one or another of a plurality of colored filters in the beam projected by the optical unit. In accordance with the standard practice in railway signaling, three filters comprising a red, a yellow and a green filter are employed in order to obtain a red, a yellow and a green indication, respectively. Although the same optical system having a source of uniform .intensity is employed to project all oi the indications, the indications are not of equal inten- C of 7% for the red filter, 12% for the green filter and for the yellow filter. This of course causes the intensities of the indications to be dependent upon'the coefiicients of transmission of the filters employed and results in a marked difference in brightness between the indications, particularly the yellow and red indications.

In view of the above-mentioned and other important considerations, it is an object of my invention to provide novel and improved means in searchlight type signals for projecting indications that have substantially uniform intensities. Another object is to provide novel and improved means for varying the intensity of the light source of a searchlight signal to compensate for the different coefiicients of, transmission of the filters employed, whereby to obtain .a

In practicing the invention, the above-men; tioned and other important objects and charac teristic features which will becomereadily appar. ent from the following description, are attained by varying the voltage of the light source inaccorde ance with the color of the indicationv to be dise played. A resistor is interposed in serieswith the signal lamp and contacts on the signal operating mechanism, or of a repeater relay thereof, shunt out a small or a large-portion of -the .resistor according as th e signal isconditioned to display its green or its yellow indication, respec tively. l

I shall describe-one form of apparatus embodying my invention, and shall then point out the novel features thereof in claims. r H

The accompanying drawingis a diagrammatic view illustrating one form of apparatus embodying my invention.

Referring to. the drawing, the reference character S designates a light signal of the searchlight type. The signal comprises an armature 5 mounted to rotate between an intermediate position to which it is biased, and two extreme positions. The armature 5 is controlled by an armature winding 6, and is polarized by thefield from a permanent magnet or an electromagnet (not shown) 'so that when the, winding 6 is energized, the armature will rotateto its right-hand or left-hand extreme position according as winding 6 is then supplied with current of normalor reverse polarity, respectively. Attached to ar mature 5 to rotate therewith are three filters or colored roundels G, R and Y, which are arranged to be disposedin the path of a beam of light. projected from an associated lamp .L acshown,- for projecting .a beam of light from the lamp. The signal indicates Proceed, Stop, or Caution, according as the filter G, R or Y is in front of lamp L when it is lighted. Operatively connected with armature 5 is a circuit controller comprising two movable contact fingers l and 8. The movable finger l cooperates with a fixed contact la to close a contact '|la when armature 5 occupies its right-hand extreme position, and with a fixed contact lb to close a contact l-lb when the armature occupies either its intermediate or its left-hand extreme position; while the movable finger 8 cooperates with a fixed contact 8m to close a contact 8--8a when armature 5 occupies its left-hand extreme position, and with a fixed contact 8b to close a contact 8-811 when the armature occupies either its intermediate or its right-hand extreme position. A signal of the type described is disclosed and covered in Letters Patent of the United States No. 1,864,224, granted June 21. 1932, to Wesley B. Wells, for Light signals.

The signal S may be controlled in any suitable manner such-as by a polarized control relay CR. The relay CR may be controlled in any suitable manner but since the control of this relay forms no part of my present invention, the control circuits for relay CR. have been omitted in order to simplify the drawing. It is deemed sufficient for the purposes of the present description to state that when relay CE is energized and its front neutral contacts II and 14 are closed, winding 6 of signal S is supplied with current of normal or reverse polarity according as polar contacts l2 and I3 of the relay occupy their normal or reverse positions, respectively. That is, when relay CR is energized and its polar contacts l2 and I3 occupy their normal or righthand positions (as viewed in the drawing), winding 6 of signal S is supplied with current of normal polarity over a normal energizing circuit which may be traced from one terminal B of a suitable source of current, such as a battery not shown, through front contact II, polar contact l2 closed in its right-hand position, winding 6 of signal S, polar contact l3 closed in its righthand position, and front contact 14 of relay CR to the other terminal C of the same source of current. When the polar contacts of relay CR are shifted to their reverse or left-hand positions and front contacts II and M are closed, winding 6 is then energized with current of the reverse polarity supplied over an obvious reverse circuit; and when relay CR is deenergized,- its front contacts winding 5.

The lamp L may be constantly lighted, as shown inthe drawing, or it may be lighted by any suitable approach control scheme only when an indication is necessary. In either event, the lighting circuit usually includes a resistor I in series with the lamp to provide a voltage control means. Ordinarily the resistor value is adjusted for the particular service conditions to be met and has a value constant for all of the indications displayed. This results in a uniform indication to be projected. As here shown, the

resistance value is controlled by means of the contacts of the signal circuit controller. Thus, for example, when winding 6 is supplied with current of normal polarity over its previously traced normal energizing circuit so that armature rotates to its right-hand extreme position wherein contacts 11a and 88b are closed and filter G is disposed in the path of the beam of II and I open to deenergize light from lamp L, the lighting circuit then extends from terminal B through circuit controller contacts 8-8b and 'L-la, a portion Illa of resistor l0 and the filament of lamp L to terminal C. When winding 6 is supplied with current of reverse polarity over its reverse energizing circuit, then armature 5 rotates to its lefthand extreme position-wherein contacts 8-811 and l'|b are closed and filter Y is disposed in the path of light from lamp L, which now is energized over a circuit extending from terminal B through contact 8-8a, portions Ilia and lb of resistor l0, and the filament of lamp L to terminal C. When, however, the energizing circuits of winding 6 are open and the winding is deenergized, then armature 5 rotates to its biased intermediate position wherein contacts 'l-lb and 88b are closed and filter R is interposed in the path of light from lamp L which is now energized over a circuit which excludes resistor l0 and which passes from terminal B through circuit controlling contacts 8-8b and 11b, and the filament of lamp L to terminal C. It follows that the value of resistance included in the lighting circuit varies from a low (zero) value through medium to a large value according as the red, green or yellow filter, respectively, is positioned in the path of the beam of light from lamp L. The intensity of the lamp is therefore automatically varied according to the color of the beam to be projected.

The particular values of the resistance inserted in circuit with lamp L when the green or yellow beams are projected, may be selected to provide compensation for the different coeflicients of transmission of the different filters so that the different beams have substantially equal intensities. If desired, however, the resistance values may be selected to provide compensation for the differences in eye response to the different colors so as to provide indications having the same apparent brightness rather than actual brightness. That is, a yellow beam of equal intensity With a red beam might appear brighter due to the superior response of the eyes to yellow color, but by properly selecting the resistance values the actual intensities of the beams may be proportioned to provide equally bright red, yellow and green beams as viewed by a person of normal color sight. In any case, the invention provides means for causing a single source of light to project a plurality of differently colored indications having relative intensities independent of the ratios of the coeflicients of transmission of the color filters employed.

Although I have hereinlshown and described only one form of light signal embodying my invention, it is understood that various changes and modifications may be made therein within the scope of the appended claims without departing from the spirit and scope of my invention.

Having thus described my invention, what I claim is:

1. In combination with a light signal comprising a plurality of differently colored filters having different coeflicients of transmission and light emitting means having a single light source for projecting a beam from said source through one or another of said filters, means for selecting the filter through which said beam is projected, and means governed by said last-mentioned means for varying the intensity of said light emitting means according to the color filter selected whereby to provide beams of different colors each having a substantially uniform intensity.

series with said source in accordance with the 2. In a searchlight signal having a single source of light and a mechanism operative to interpose in the path of the beam from said source one or another of a plurality of differently colored filters each having a different coeflicient of transmission, means governed by said mechanism for varying the intensity of said source in accordance with the particular filter interposed in the path of said beam to provide beams having relative intensities independent of the ratios of the said 10 coefficients of transmission of said filters.

3. In a Searchlight signal having a single source of light and a mechanism for interposing in the a path of the beam projected from said source one or another of a plurality of diiferently colored filters having'different coeflicients of transmission, a resistor in series with said light source, and means controlled by said mechanism for varying the effective value of said resistance in color of the filter interposed in said light beam. 20

4. In a light signal having a source of light and a mechanism for selectively interposing a red, a green or a yellow filter in the path of the beam from said source, the combination therewith of means controlled by said mechanism for providing a relatively high, a medium, or a relatively low intensity for, said source according as said red, green or yellow filter is interposed in said beam respectively.

5. In a light signal having an electric lamp and a mechanism for selectively interposing a red, a green or a yellow filter in the path of the beam from said lamp, the combination therewith of means controlled by said mechanism for interposing a minimum, an intermediate, or a maximum value of resistance in series with said lamp according as said red, green or yellow filter is interposed in said beam respectively.

GEORGE R. PFLAS'I'ERER. 

